DOCS.
108,
109 JULY 1908 79
Please
write
me
what
you
think of
it
because
this is
the
only
encouragement
I have.
What
we are
constructing
first
is
not
that but
this
//////*
///////S/S/S/SSSsss/s
1
approx.
natural size
But the
quantity
of
air called for
is
also
greater
in
a
fast-running pump
with
such
a
tube.
One
always
has
then
a
Hg plug
that
shuts off
a
considerable
amount
of
air.
The rotational
veloc.
is
high
the
cross
section
constant
and
somewhat
larger
only
at
the
air
inlet tube
orifice.
109.
To
August Hagenbach
Bern, 6
July
1908
Highly
esteemed
Professor
Hagenbach:[1]
When
I
made
your
acquaintance
in
Zurich
a
few weeks
ago,[2]
you
told
me
that the
area
of
your
special
interest
is
spectroscopy.[3]
Hence
questions dealing
with
light
interference
surely are
also within
your purview.
I
therefore take the
liberty
of
asking
you a
question
from this
area
with which I have
been
struggling
for
a long
time.-
Suppose a ray
bundle
is decomposed-say
by
partial
reflection
at
a
thin
silver
layer,
into two
completely
coherent
(capable
of
interference)
beams.
Does the
capacity
of
these beams
to
interfere
with
one
another remain
complete
if
each of the
two is
attenuated
to
the
same
extent
by absorption?[4]
According
to
the
customary
theoretical
representation,
which ascribes
the
absorption
to
(friction-)
terms
that
are
proportional
to the
velocity
of the
material carrier of the
motion of
light,
one
would
naturally
have to conclude
that
the
capacity
to
interfere
does
not
diminish. But since
these
terms
can only
be viewed
as a stopgap,
and
since,
in truth,